1. Field of the Invention
This invention relates to cooling of components having non-film cooled hot surfaces for disposal and use in a hot flowpath, and more particularly, to components used in gas turbine engines including hot compressor blades and turbine vanes and blades having non-film cooled hot surfaces.
2. Description of Related Art
It is well known to cool parts using heat transfer across walls having hot and cold surfaces by flowing a cooling fluid in contact with the cold surface to remove the heat transferred across from the hot surface. Among the various cooling techniques presently used are convection, impingement, and film cooling. These cooling techniques have been used to cool gas turbine engine hot section components such as turbine vanes and blades. Film cooling has been shown to be very effective but requires a great deal of fluid flow which typically rewires the use of power and is therefore generally looked upon as fuel efficiency and power penalty in the gas turbine industry.
When turbine components are exposed to a high temperature gas flow, the surface heat transfer coefficient is inversely proportional to the boundary layer thickness. On airfoil surfaces, the boundary layer grows from the leading edge stagnation point toward the trailing edge. Therefore, the boundary layer thickness is small and the heat transfer coefficient is high near the leading edge of the airfoil. Film cooling holes at the leading edge have often been used to cool the leading edge of the airfoil. It is highly desirable to have a means for altering the boundary layer thickness and reduce the heat transfer coefficient near the leading edge.
Another drawback to film cooling is the degree of complexity in fabricating and machining the components. In the past, film cooling techniques have been developed. Turbine airfoils on both blades and vanes often incorporate film cooling holes and slots to flow cooling air along the hot surfaces of the airfoil walls. Film cooling slots and angled holes require a great deal of fabrication and or machining. The wall structures themselves are weakened by the cooling airflow passages required to flow the cooling air from the cold to the hot surfaces.
The present invention was developed to improve non-film cooling techniques for gas turbine engine hot section components so as to efficiently cool the components without resorting to film cooling and the drawbacks discussed above that are associated with such techniques.